The present invention relates to an individual rear suspension having a lifting device for a vehicle. The individual rear suspension is especially suitable to be used in a rear suspension arrangement having a pusher function.
Heavy vehicles are normally provided with front wheels suspended on a rigid front axle and steering knuckles. The front axle is an integral unit often made of heat treated, drop-forged special steel. The rear wheels are normally also suspended with a rigid rear axle. For a driven rear axle, a rear axle housing is used both for suspending the wheels and for the transmission of power from the drive train to the wheels, where the rear axle housing is provided with a differential and drive shafts.
Heavy vehicles are often provided with more than one rear axle. Depending on the intended use, the additional rear axles may be either driven or trailing and they may be fixed or steerable. When more than one axle is used, they are often arranged in a bogie configuration.
The purpose of the rear suspension is to absorb the forces that arise when the driving three of the wheels is transferred to the road surface. At the same time, it must also support the major part of the total weight of the vehicle. A vehicle can be equipped with a single rear axle, or with a bogie consisting of or comprising two or three rear axles. The bogie can he composed of two driving rear axles (6×4) or with one driving rear axle and a trailing, wheel axle (6×2). Bogie combinations with two trailing wheel axles, one in from and one behind the driving wheel axle, also appear. Some trailing wheel axles can be raised and lowered with the aid of a bogie lift.
A trailing axle is used strictly for load-bearing purposes and can be raised when it is not required. A trailing axle located immediately in front of a drive axle is called a pusher axle and a trailing axle situated behind a drive axle is called a tag axle. When a trailing axle is not used, e.g. when the vehicle is empty, it can be raised in order to improve the drivability of the vehicle and to reduce wear on the axle and its components. Designing a lifting tag axle having a rigid axle is relatively easy, since the tag axle will not interfere with the propeller shaft of the vehicle.
Often, a pusher axel consists of r comprises a front axle with steering knuckles installed in front of the driving rear axle. This type of bogie appears in two different models, one with a steerable pusher axle and one with a locked pusher axle. In the model with the steerable pusher axle, the steering knuckles are connected to the front axle steering function. For the locked pusher axle, the steering knuckles are fixed in one position. One problem with raising a pusher axle is that the axle will interfere with the propeller shaft. The front axle normally extends downwards, such that there is room for the propeller shaft when the pusher axle is raised. This solution however reduces the ground clearance of the vehicle, since the axle must be positioned below the propeller shaft.
There is thus room for an improved individual rear suspension arrangement.
It is desirable to provide an improved individual suspension for a liftable rear axle. It is also desirable to provide an improved rear suspension arrangement for a liftable rear axle with a reduced extension in a longitudinal direction. It is also desirable to provide an improved rear suspension arrangement which reduces stress imposed on the main frame of the vehicle. It is also desirable to provide an improved rear suspension arrangement having an improved ground clearance. It is also desirable to provide a method for mounting the improved rear suspension arrangement to the vehicle.
The solution to the problem according to the invention is described in the characterizing part of claim 1 with regards to the individual rear suspension, in the characterizing part of claim 7 with regards to the individual rear suspension arrangement, in claim 14 with regards to the vehicle and in claim 17 with regards to the method. The other claims contain advantageous further developments of the inventive rear suspension and the method.
In an individual suspension for a rear axle of a vehicle, comprising a lower wishbone bracket and an upper wishbone bracket, where the lower wishbone bracket and the upper wishbone bracket are hingedly suspended to a support assembly and to a kingpost, the suspension further comprises an air bellows and a lifting bellows.
By this first embodiment of the individual suspension according to the invention, an individual suspension for a liftable rear axle is provided which have a reduced extension in the longitudinal direction of the suspension. The air bellows and the lifting bellows are arranged sideways to each other, along the centre line of the imaginary wheel axle of the suspension. In this way, the suspension arrangement does not extend forwards or rearwards of the wheel, which e.g. allows for the use of a larger fuel tank. The suspension is hingedly suspended in a support assembly which is preferably attached to a frame bracket and not directly to the main frame of the vehicle. Preferably, the air bellows and the lifting bellows are also supported by the same frame bracket.
The actual suspension of a wheel is obtained by the use of two wishbone brackets, an air bellows and a king post which holds and supports the wheel. Both wishbone brackets are hingedly suspended in the support assembly and in the king post. The support assembly, which may be a sub-frame assembly, is preferably fixedly mounted to a single frame bracket, which means that the support assembly is fixed when the wheel springs. With all load carrying components of the suspension mounted to the same flame bracket, and with the frame bracket mounted to the web of the main frame beam in only one mounting position, no loads acting on the wheel suspension will be transferred to the main frame beam but will be absorbed and diverted by the frame bracket.
The air bellows is positioned outside the vehicle frame, outside of a plane defined by the web of the main frame beam. The lifting bellows is positioned inside the vehicle frame, inside of a plane defined by the web of the main frame beam. In this way, both the air bellows and the lifting bellows are well protected and the longitudinal extension of the wheel suspensions is reduced compared to commonly known lifting arrangements.
In an individual suspension arrangement for a liftable rear axle of a vehicle, comprising a left wheel suspension and a right wheel suspension, the arrangement further comprises at least one sub-frame assembly extending between the left and right wheel suspensions, where the left and right wheel suspensions are mounted directly to the sub-frame assembly.
By this first embodiment of the individual suspension arrangement according to the invention, a rear suspension is provided in which each wheel can move independently of the other. The wheel suspension is provided with an air bellows and a lifting bellows which further allows for a reduced extension in the longitudinal direction of the suspension arrangement. In this way, the suspension arrangement does not extend forwards or rearwards of the wheel, which e.g. allows for the use of a larger fuel tank. In the suspension, the left and right wheel suspensions are connected to each other with a sub-frame assembly which is fixed in position and does not move when the wheels spring. Preferably, the sub-frame assembly comprises two sub frames.
Each individual suspension is mounted to a sub-frame assembly which is fixed when the wheel springs. The sub-frame assembly is mounted to frame brackets, where one frame bracket is mounted on each side of the vehicle frame. The frame brackets are mounted only to the web of the main frame beams, and are mounted only in one mounting position. In this way, no loads acting on the wheel suspension will be transferred through the main frame beams but will be absorbed in the rear suspension arrangement. The lifting bellows acts on an extension of the lower wishbone bracket. Since each lifting bellows act on each individual wheel suspension, the sub-frame is fixed also when the wheels are raised. In this way, there will be no interference between the sub-frame and the propeller shaft. Further, the ground clearance of the vehicle may be improved.
In the method for mounting the rear suspension arrangement, a rear suspension assembly comprising the sub-frame assembly and the right and the left wheel suspensions is preassembled. The frame brackets are mounted to the web of the main frame beams, one on each side. Thereafter, the rear suspension assembly is docked to the frame brackets and is mounted to the frame brackets in four mounting positions, two spaced apart mounting positions on each frame bracket.